Controlled discharge gas vent

ABSTRACT

A fire protection system includes a dry pipe system and a controlled discharge gas vent. The dry pipe system and controlled discharge gas vent operate using a breathing cycle to displace oxygen and/or water vapor from within the piping network of the dry pipe system. The controlled gas discharge vent allows displacement of pressurized air with nitrogen, for example, using manual or automated processes that can employ one or more sensors. Corrosion resulting from oxygen, water, and/or microbial growth is reduced or nearly eliminated.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a division of U.S. patent application Ser.No. 12/606,287, filed Oct. 27, 2009, the disclosure of which is herebyincorporated herein by reference in its entirety.

INTRODUCTION

The present technology relates to a vent and venting methods for thecontrolled discharge of gas, where the vent and methods can be used in afire protection system and can operate to automatically vent a dry pipeor preaction system.

A fire protection system, also known as a fire suppression or firesprinkler system, is an active fire protection measure that includes awater supply to provide adequate pressure and water flow to a waterdistribution piping system, where water is discharged via sprinklers ornozzles. Fire protection systems are often an extension of existingwater distribution systems, such as a municipal water system, waterwell, water storage tank, or reservoir. Fire protection systems can beseparated into two general types, wet pipe systems that include a pipingnetwork prefilled with water, and dry pipe systems that include at leasta portion of the piping network filled with air/gas instead of water.

Dry pipe sprinkler systems can be used where the fire protection systemmay be exposed to freezing temperatures. A typical dry pipe sprinklersystem includes a preaction/dry pipe sprinkler network containing aplurality of normally closed sprinkler heads. The sprinkler network isconnected via a piping system to a dry pipe valve or primary watersupply valve which has a dry output side facing the piping system and awet input side facing a pressurized source of water. In standbyoperation, the piping system and sprinkler network are filled or chargedwith a gas, such as air, which may be pressurized. Industrial dry pipesystems generally charge the piping system lines to about 25 to 50 psig.The sprinkler heads typically include normally closedtemperature-responsive elements.

If heated sufficiently, the normally closed element of the sprinklerhead opens, allowing pressurized gas to escape from the piping system.As gas pressure in the fluid flow lines drops below a predeterminedvalue, a mechanism causes the dry pipe valve to open. Pressurized waterthen flows into the piping system, displacing the gas, and exits throughthe open sprinkler head to extinguish the fire or smoke source. Waterflows through the system and out the open sprinkler head, and any othersprinkler heads that subsequently open, until the sprinkler head closesitself, if automatically resetting, or until the water supply is turnedoff.

There are a number of different mechanisms and techniques for causing adry pipe sprinkler system to go “wet;” i.e., to cause the primary watersupply valve to open and allow the water to fill the piping systemlines. In one mechanism, after a sprinkler head opens, the pressuredifference between the gas pressure in the piping system and the watersupply pressure on the wet side of the primary water supply valve mustreach a specific hydraulic imbalance before the primary water supply canopen.

Maintenance of the air or gas pressure in the fluid flow lines isimportant for proper operation of the dry pipe system. On one hand, ifgas pressure drops too low, for example, where there is a leak in thepiping system, the dry pipe valve may be unable to maintain the specifichydraulic balance necessary to prevent the dry pipe valve from openingand allowing water to enter the piping system. The system must then bedrained and recharged. On the other hand, if the pressure is too high inthe piping system, there may be a significant delay in opening the drypipe valve to allow water to enter the fluid flow lines and reach one ormore sprinklers, as the excess pressure must be vented prior to openingthe water supply. Dry pipe sprinkler systems can also suffer from falsealarms from ambient temperature-induced expansion and contraction of thepressurized air within the fluid flow lines. For example, thepressurized gas may contract to a degree that triggers opening of theprimary water valve.

SUMMARY

The present technology includes various apparatuses and methods forventing and controlling corrosion in fire protection systems.Embodiments include controlled discharge gas vents that comprise aliquid sensing valve having (1) an inlet and an outlet, (2) a backpressure regulator having an inlet and an outlet, and (3) an orificehaving an inlet and an outlet, operable to provide a flow rate of gastherethrough. The inlet of the back pressure regulator is coupled to theoutlet of the liquid sensing valve. The inlet of the orifice coupled tothe outlet of the back pressure regulator. The vent may include one ormore sensors, such as an oxygen sensor and/or a humidity sensor. Theback pressure regulator may be operable to continuously provide a lowflow of gas to the orifice and provide a high flow of gas to the orificeupon reaching a pressure threshold. The pressure threshold may beadjustable.

Embodiments also include fire protection systems that comprise asprinkler system and a source of pressurized gas coupled to thesprinkler system. The sprinkler system comprises at least one sprinkler,a source of pressurized water, a piping network connecting the at leastone sprinkler to the source of pressurized water, and a controlleddischarge gas vent. The sprinkler system may be a dry pipe system or apreaction system. And the source of pressurized gas may be provided byan air compressor and/or a nitrogen generator.

Embodiments further include methods of reducing corrosion in a fireprotection system. The piping network of the sprinkler system ispressurized with the source of pressurized gas to provide a pressurethat prevents the dry pipe valve from opening or maintains the amount ofpressurized gas in a preaction system to supervise the integrity of thepiping network. The pressure is further increased using the source ofpressurized gas to exceed a threshold pressure of the back pressureregulator of the controlled discharge gas vent, where the thresholdpressure of the back pressure regulator is greater than the pressurethat prevents the dry pipe valve from opening. The pressurized gas isthen vented via the controlled discharge gas vent by opening of the backpressure regulator until the pressure of the piping network is below thethreshold pressure of the back pressure regulator, whereupon the backpressure regulator closes.

The pressure within the piping network may be increased another time,causing the pressure to again exceed the threshold pressure of the backpressure regulator of the controlled discharge gas vent. The pressurizedgas is then vented via the controlled discharge gas vent by opening ofthe back pressure regulator until the pressure of the piping network isbelow the threshold pressure of the back pressure regulator. Thesepressurization and depressurization cycles (“breathing” cycles) may berepeated so that the pressurized gas, which may be compressed air and/ornitrogen for example, effectively displaces substantially all thehumidified air/moisture and/or oxygen within the piping network.

DRAWINGS

The present technology will become more fully understood from thedetailed description and the accompanying drawings.

FIG. 1 illustrates an embodiment of a controlled discharge gas ventconstructed according to the present disclosure.

FIG. 2 illustrates an embodiment of a controlled discharge gas ventcoupled to a fire protection system and coupled to an oxygen sensor andalarm constructed according to the present disclosure.

FIG. 3 illustrates an embodiment of a fire protection system comprisinga dry pipe sprinkler system having a controlled discharge gas ventconstructed according to the present disclosure.

It should be noted that the figures set forth herein are intended toexemplify the general characteristics of apparatus, systems, and methodsamong those of the present technology, for the purpose of thedescription of specific embodiments. These figures may not preciselyreflect the characteristics of any given embodiment, and are notnecessarily intended to define or limit specific embodiments within thescope of this technology.

DETAILED DESCRIPTION

The following description of technology is merely exemplary in nature ofthe subject matter, manufacture and use of one or more inventions, andis not intended to limit the scope, application, or uses of any specificinvention claimed in this application or in such other applications asmay be filed claiming priority to this application, or patents issuingtherefrom. The following definitions and non-limiting guidelines must beconsidered in reviewing the description of the technology set forthherein.

The headings (such as “Introduction” and “Summary”) and sub-headingsused herein are intended only for general organization of topics withinthe present disclosure, and are not intended to limit the disclosure ofthe technology or any aspect thereof. In particular, subject matterdisclosed in the “Introduction” may include novel technology and may notconstitute a recitation of prior art. Subject matter disclosed in the“Summary” is not an exhaustive or complete disclosure of the entirescope of the technology or any embodiments thereof. Classification ordiscussion of a material within a section of this specification ashaving a particular utility is made for convenience, and no inferenceshould be drawn that the material must necessarily or solely function inaccordance with its classification herein when it is used in any givencomposition.

The description and specific examples, while indicating embodiments ofthe technology, are intended for purposes of illustration only and arenot intended to limit the scope of the technology. Moreover, recitationof multiple embodiments having stated features is not intended toexclude other embodiments having additional features, or otherembodiments incorporating different combinations of the stated features.Specific examples are provided for illustrative purposes of how to makeand use the apparatus and systems of this technology and, unlessexplicitly stated otherwise, are not intended to be a representationthat given embodiments of this technology have, or have not, been madeor tested.

As used herein, the word “include,” and its variants, is intended to benon-limiting, such that recitation of items in a list is not to theexclusion of other like items that may also be useful in the materials,compositions, devices, and methods of this technology. Similarly, theterms “can” and “may” and their variants are intended to benon-limiting, such that recitation that an embodiment can or maycomprise certain elements or features does not exclude other embodimentsof the present technology that do not contain those elements orfeatures.

“A” and “an” as used herein indicate “at least one” of the item ispresent; a plurality of such items may be present, when possible.“About” when applied to values indicates that the calculation or themeasurement allows some slight imprecision in the value (with someapproach to exactness in the value; approximately or reasonably close tothe value; nearly). If, for some reason, the imprecision provided by“about” is not otherwise understood in the art with this ordinarymeaning, then “about” as used herein indicates at least variations thatmay arise from ordinary methods of measuring or using such parameters.In addition, disclosure of ranges includes disclosure of all distinctvalues and further divided ranges within the entire range.

The present technology relates to a controlled discharge gas vent thatcan be used as an automatic vent in a dry pipe or preaction firesprinkler system. The vent can provide for the controlled discharge ofgas from pressurized fire sprinkler system piping, such as employed indry pipe or preaction sprinkler systems. In some aspects, the controlleddischarge gas vent can allow for progressive displacement of pressurizedgas initially contained in a fire sprinkler system piping network withanother gas. For example, pressurized air may be displaced with a drierpressurized gas, i.e., a gas having a lower water vapor content, such asdehumidified air or dry nitrogen gas produced from a nitrogen generator,for example, as disclosed by International Application No.PCT/US09/56000, Burkhart et al., filed Sep. 4, 2009. The controlleddischarge gas vent may also be used to provide the controlled dischargeof any gas for displacement with another gas while maintaining anacceptable pressure within a system that is being vented.

Aspects of the controlled discharge gas vent can provide for preciserelease of a quantifiable amount of gas at a known rate of dischargeover time within a given pressure range. This is accomplished throughthe use of one or more vents including particular orifices that may belocated at various locations within the fire sprinkler system pipingnetwork, for example. These discharge orifices may comprise particularmachined metallic orifices having specific apertures. In someconfigurations, gas is discharged from a pipe or piping network havingan internal pressure higher than atmospheric pressure (14.7 psi) toatmospheric pressure at the discharge orifice. The pressure drop may bedetermined at the discharge orifice. With a known differential pressureand a known orifice diameter, it is possible to determine the amount ofgas that will be discharged per unit of time, typically in standardcubic feet per minute.

The controlled discharge gas vent may be used as part of a fireprotection system, such as a dry pipe sprinkler system. Basically, thereare two predominant types of automatic fire protection sprinklersystems—a wet pipe system wherein the piping leading from its watercontrol valve to the sprinkler heads is normally filled with water, anda dry pipe system wherein the piping leading from its water controlvalve to the sprinkler heads is pressurized with a gas until the watercontrol (dry pipe) valve, closing off the source of water from thesystem, is opened to introduce water into the piping leading to thesprinkler heads thereof. On one hand, wet pipe sprinkler systems offerthe advantage of water being immediately discharged from an operatedsprinkler. On the other hand, wet pipe sprinkler systems cannot bereadily used in applications where there is a possibility that thesystem piping interconnecting the sprinkler(s) will be exposed tofreezing temperatures. Accordingly, dry pipe sprinkler systems arenormally used in applications where freezing temperatures may occur. Drypipe sprinkler systems, however, have the drawback that because thepiping system is normally filled with pressurized gas and not water,water is not immediately discharged from an operated sprinkler.

Sprinkler systems are preferably engineered to meet the standards of theNational Fire Protection Association (Quincy, Mass. USA; see N.F.P.A.Pamphlet 13, “Standard for The Installation of Sprinkler Systems”),Factory Mutual (F.M.), Loss Prevention Council (Johnston, R.I., USA),Verband der Sachversicherer (Köln, Germany), or other similarorganizations, and also comply with the provisions of governmentalcodes, ordinances, and standards where applicable.

In dry pipe sprinkler systems, when a sprinkler head is operated, aportion of the pressurized gas flows out through the opened sprinklerhead, causing a decrease in the pressure of the gas in the pipingsystem. When the pressure of the gas in the piping drops to a certainlevel, a dry pipe valve automatically opens so that water can beintroduced into the piping. However, because gas is a compressiblemedium, it may take a relatively substantial amount of time for thepressure of the gas in the piping to decay to a level which issufficient to open the dry pipe valve.

When a fire occurs, it is critical that water be quickly delivered to anoperated sprinkler. For example, National Fire Protection AssociationStandard N.F.P.A. Pamphlet 13 requires that dry pipe sprinkler systemsbe constructed such that when the sprinkler head furthest from the drypipe valve is operated, water will be delivered thereto within sixtyseconds of the time of operation. For this reason, a dry pipe sprinklersystem may require an accelerator which is utilized for sensing a slightbut significant rate of decay in the dry pipe system gas pressure andfor quickening the opening of the dry pipe valve connected thereto, inresponse to the pressure decay.

A differential type of a dry pipe valve may be constructed with twochambers: a main chamber that is exposed to system pressure and anintermediate chamber that is normally exposed to atmospheric pressure.Further, a differential type of dry pipe valve can be designed such thatwhen a fluid under a pressure of essentially the same value as the gasin the system is admitted to the intermediate chamber, the channelbetween the source of water supply and the system will be opened. Anaccelerator may be interconnected by piping between its inlet and thepressurized portion of the system and between its outlet and theintermediate chamber of the dry pipe valve such that when theaccelerator is actuated, gas under pressure is admitted from the systemto the intermediate chamber of the dry pipe valve to effect the openingof the latter. Once water has been introduced into a dry pipe sprinklersystem by opening of its dry pipe valve, the water can freely passthrough the piping system leading to the sprinkler heads.

A type of dry pipe sprinkler system is a preaction system. Preactionsprinkler systems may be used in locations where accidental waterdischarge could result in significant property damage due to thepresence of water-sensitive materials or equipment. Preaction systemsare hybrid systems of wet and dry systems, and can include singleinterlock and double interlock features.

Operation of the single interlock system is similar to dry systemsexcept that these systems require that a preceding fire detection event,typically the activation of a heat or smoke detector, takes place priorto the action of water introduction into the system's piping by openingthe preaction valve, which can be an automatic, mechanically actuatedvalve. Opening the valve converts essentially a dry system into a wetsystem. The intent is to reduce the undesirable time delay of waterdelivery to sprinklers that is inherent in dry systems. Prior to firedetection, if the sprinkler operates or the piping system develops aleak, loss of air pressure in the piping can activate a trouble alarm.In this case, the preaction valve does not open due to loss ofsupervisory pressure, and water will not enter the piping.

Double interlock systems employ automatic sprinklers. These systemsdetect a preceding event, typically the activation of a heat or smokedetector, and also include operation of an automatic sprinkler prior tothe action of water being introduced into the piping system. Activationof just the fire detectors alone or just the sprinklers alone, withoutthe concurrent operation of the other, does not allow water to enter thepiping system. Double interlock systems are considered essentially drysystems in terms of water delivery times.

The controlled discharge gas vent can provide a means for maintainingcontrol of the pressure within the fire sprinkler system piping networkwhile at the same time providing for the controlled discharge of ameasured amount of gas that is contained in the fire sprinkler systempiping network. The vent allows the fire sprinkler system piping systemto “breathe,” where for example a gas having lower relative humidity,such as dehumidified air or dry nitrogen gas, is admitted to the pipingnetwork during a pressuring-up phase and a mixture of gases (e.g.,containing the dehumidified air or nitrogen) and a portion the originalgas that was contained in the piping system is vented during apressuring-down phase. The pressure within the fire sprinkler systempiping network is therefore maintained in a controllable range ofpressures throughout the breathing process called the “breathing range.”

The controlled discharge gas vent can be used to reduce corrosion in thefire protection system. Oxygen present in air and water vapor presentwithin the fire protection system can be vented from the system andeffectively displaced by using the controlled discharge gas vent inconjunction with one or more breathing cycles to purge the system fromsubstantially all oxygen or to reduce the amount of water vaporcontained in the gas within the piping system. For example, oxygenand/or water vapor may be displaced with dry nitrogen provided by anitrogen generator. Removal of oxygen and/or water vapor reduces oreliminates the effects of oxidative corrosion of ferrous and cuprouscomponents of the fire protection system and can further deprive aerobicmicrobiological organisms the opportunity to grow within the system.Curtailing the growth of aerobic microbiological organisms serves tolimit another source of corrosion and can limit solids and debris withinthe system.

Oxygen and/or water vapor within the fire protection system may bepresent in pressurized air used to maintain the dry pipe valve shutuntil the system is actuated. For example, initial pressurization of thedry pipe system can be done using an air compressor to rapidly fill thedry piping network above the trip pressure. Testing or actuation of thesystem also introduces water, including dissolved oxygen, into thepiping network, resulting in residual liquid water that pools in lowspots of the piping network and/or resulting from condensation of watervapor within the piping network. Use of the controlled discharge gasvent and breathing cycle(s) can significantly reduce or eliminatecorrosion in the dry pipe system. For example, as oxygen is often theprimary corrosive specie within the system, displacement of a largepercentage of the oxygen with noncorrosive nitrogen by using thecontrolled discharge gas vent and breathing cycle can preserve theintegrity and hydraulics of the fire protection system.

An embodiment of the breathing process employing the controlleddischarge gas vent is illustrated by the following steps.

Step 1: The fire sprinkler system piping network sits empty atatmospheric pressure, i.e., about 14.7 psi, filled with air whichcontains approximately 78% nitrogen gas and 21% oxygen gas.

Step 2: The fire sprinkler system piping network is pressurized withcompressed air to attain at least a sufficient pressure within thepiping system to prevent the dry pipe valve from opening, which wouldallow water from the upstream side of the dry pipe valve to enter thefire sprinkler system piping network. The pressure at which the dry pipevalve would actuate and open is called the “trip pressure.” For example,the trip pressure for the valve may be about 25 psig. Therefore, as longas the pressure in the fire sprinkler system piping network ismaintained above 25 psig, then the dry pipe valve will not actuate andwater will not enter the fire sprinkler system piping network.

Step 3: The fire sprinkler system piping network is pressurized withadditional compressed air to achieve a pressure of about 40 psig, forexample. This pressure is the “high limit” pressure of the breathingrange. At this pressure the introduction of additional compressed air isstopped.

Step 4: One or more controlled discharge gas vents within the firesprinkler system piping network are opened to allow gas to escape fromthe system. As a result, the pressure drops incrementally from 40 psig.The gas continues to vent from the fire sprinkler system piping networkat a rate that is controlled by the vent(s) while preventing the suddendepressurization of the system. This controlled release of gas and theresultant drop in fire sprinkler system piping network pressurecontinues until the system pressure drops to about 30 psig, for example.This pressure is the “low limit” pressure of the breathing range, whichis above the trip pressure. At this point, the nitrogen generatorpneumatic pressure switch senses the low limit pressure and opens acontrol valve in the nitrogen generator to begin repressurizing the firesprinkler system piping network with compressed gas having reducedhumidity relative to the compressed gas within the piping network; e.g.,dry nitrogen gas of purity greater than or about 90%. As illustrated,the breathing range in the present example is from 30 psig up to 40psig. All of the breathing takes place at a pressure that exceeds theminimum trip pressure of the dry pipe valve, which is 25 psig in thepresent example.

Step 5: Pressurized gas having reduced humidity, such as nitrogenproduced from a nitrogen generator, or some acceptable nitrogen gasstorage vessel, is pumped into the fire sprinkler system piping networkuntil the pressure in the system reaches the high limit pressure of thebreathing range. At this point, the nitrogen generator pneumaticpressure switch senses the high limit pressure and closes a controlvalve in the nitrogen generator to stop pressurizing the fire sprinklersystem piping network with the compressed nitrogen gas. This completesone breathing cycle.

Step 6: During the pressurizing and depressurizing process (i.e.,breathing), one or more of the controlled discharge gas vents may remainopen to allow for the continuous discharge of a controlled amount ofmixed gases (e.g., air and enriched nitrogen) from the fire sprinklersystem piping network.

Step 7: With every breathing cycle, the gas composition within the firesprinkler system piping changes as water vapor within the piping networkis displaced with gas having a lower relative humidity. For example,purified nitrogen gas (of at least about 90% purity, for example) can beadded to the fire sprinkler system piping network during thepressurizing phase of the breathing cycle and the mixed gas (residualpressurized air plus the added nitrogen) discharged from the systemduring the depressurizing phase of the breathing cycle. Over a period oftime, the gas composition within the fire sprinkler system pipingnetwork gets closer and closer to the composition of the introduced gashaving lower relative humidity; e.g., purified nitrogen gas added fromthe nitrogen generator.

The rate of gas discharge and the changeover in the composition of thegas within the fire sprinkler system piping network from 100% air toabout 90% nitrogen (or higher), for example, is controlled by thebreathing range pressures, the number and location of vents installed onthe fire sprinkler system piping network, and the size of the orificesthat are installed in the vents. It is possible to accurately determinethe number of cycles and the time required to achieve a purity of about90% nitrogen (or higher) throughout the fire sprinkler system pipingnetwork. See the vent breathing rate calculation examples presented inTable 1.

TABLE 1 Vent Breathing Rate Calculator Parameter Value Units OperationSprinkler system capacity 800 gallons (gallons) Sprinkler systemcapacity (ft3) 106.9 ft 3 Converts gallons to standard cubic foot (SCF)Equivalent SCF @ (psig) 25 288.8 scf Converts volume to volume at highend breathing pressure Equivalent SCF @ (psig) 18 237.9 scf Convertsvolume to volume at low end breathing pressure Difference (to be ventedper 50.93 scf Amount of gas vented between low end and cycle) high endVent rate from one #10 orifices 2.92 scfh Venting rate of gas from #10orifice at 20 psig Vent rate from one #8 orifices 1.80 scfh Venting rateof gas from #8 orifice at 20 psig Vent rate from one #5 orifices 0.70scfh Venting rate of gas from #5 orifice at 20 psig Total venting rate5.42 scfh Total venting rate Time for venting step 9.40 hrs Total amountof time (hrs) to vent the 50.93 scf from the system Time for ventingstep 563.8 mins Total amount of time (min) to vent the 50.93 scf fromthe system Estimated Membrane N2 4% 155 scfh Total amount of nitrogendelivered per hour production rate at 75 deg F. and from generator 85psig Net filling rate at 75 deg F. and 149.6 scfh Total amount ofnitrogen delivered per hour 96% less bled during filling Time for fillstep 0.34 hr Length of time required to fill the vent gas back up in thesystem Total system venting cycle 9.74 hr Total cycle of venting andfilling time

TABLE 2 Orifice-Pressure Measurements for Calculations in Table 1Orifice Orifice Orifice Orifice Orifice Orifice PRESS #4 #5 #8 #10 #12#19 10 psig 0.25 0.47 1.21 1.97 2.73 6.00 20 psig 0.40 0.70 1.80 2.924.07 9.03 25 psig 0.47 0.82 2.08 3.37 4.66 10.40

The controlled discharge gas vent may include additional features. Forexample, in order to control the rate of gas discharge from the pipethrough the orifice, it is necessary to prevent plugging of the metalorifice. Pipelines routinely contain debris, corrosion byproduct,mineral scale, and other solid or semi-solid material that might blockgas flow through the discharge orifice. Therefore, an in-line filter maybe used to protect the orifice from possible blockage by debris.

In order to prevent discharge of water through the vent from the firesprinkler system piping network during a fire response, a liquid sensingvalve may be included. For example, a liquid sensing valve can include alevered float valve or an electric liquid sensing control unit. Whilegas is flowing through the fire sprinkler system piping network, theorifice in the float valve allows for gas to flow freely. In the eventof a fire response, water will fill the fire sprinkler system pipingnetwork. When water reaches the liquid sensing valve, such as a floatvalve, an internal float rises on the incoming water to actuate alevered plug which seats on an elastomeric seal at the orifice. Thisaction stops the flow of gas and water from the pipeline through thecontrolled discharge gas vent.

In order to prevent plugging of the float valve orifice, an in-line“Y”-strainer may be installed upstream of the float valve to capture anydebris, corrosion by-product, mineral scale, or any other solid orsemi-solid material that might block the gas or water flow through thefloat valve orifice.

Two other components may be included in the controlled discharge gasvent to provide for ease of installation and servicing of the vent. Thefirst is an isolation ball valve and the second is a union.

An embodiment of the controlled discharge gas vent 100 constructedaccording to the present disclosure is shown in FIG. 1. The various ventcomponents and their specific functions are illustrated as follows. Aball valve 110 provides isolation of the controlled discharge gas vent100 from the fire sprinkler system piping (not shown), which ispressurized and provides the gas flow 105. A coupling union 115 provideseasy installation or change out of the vent 100. A Y-strainer typefilter 120 protects a metallic orifice 145 at the discharge of a leveredfloat valve 125 from plugging with pipe debris. The levered float valve125 or equivalent electric liquid sensing control unit allows gasdischarge from the piping system but not liquid discharge; water can beprevented from flowing out of the vent 100 location if the floatactivates when liquid enters the valve 125 by sealing the dischargeorifice. A gas sampling port 130 allows for gas analysis using a manualor automatic gas sampling device. An in-line filter 135 protects theend-of-line metallic orifice 145 from plugging with debris. Anadjustable back pressure regulator 140 with a gauge prevents completedepressurization of the fire sprinkler system piping by automaticallyclosing the vent 100 if the system pressure falls below a preset minimumpressure on the regulator 140. The preset minimum pressure can be set ata pressure above the trip pressure of the dry pipe valve by setting aminimum closing pressure that is above the trip pressure of the dry pipevalve. The end of line metallic orifice 145 provides for the controlledrelease of gas from the pressurized piping system. And an end of linemuffler 150 may be used to deaden the sound of the gas exhaust 155.

Discharge rate of gas, e.g., in standard cubic feet per hour (SCFH),from the vent can be controlled using orifices having particulardiameters. For example, such orifices can employ a one-piececonstruction of solid metal; e.g., brass or stainless steel. Suitableorifices are available from O'Keefe Controls Co., Trumbull, Conn.Accurate machining allows predictable discharge rates based on theorifice diameter. Typical sizes range from 0.004″ to 0.125″ in orificediameter, which are given a number (#) designation, for example. Table 3lists some typical orifice sizes and Table 4 lists air flow in SCFH;these orifice sizes and flow rates are illustrative only as larger orsmaller orifices may be employed depending on the particular needs anddesign of the vent and system.

TABLE 3 Orifice Sizes Orifice Diameter Size Number (inch) 4 .0039 5.0051 6 .0059 7 .0071 8 .0079 9 .0091 10 .0102 11 .0110 12 .0122 13.0130 14 .0142 15 .0150 16 .016 17 .017 18 .018 19 .019 20 .020 21 .02122 .022 23 .023 24 .024 25 .025

TABLE 4 Metal Orifice Air Flow—SCFH Orifice  0.004  0.005  0.006  0.007 0.008  0.009  0.010  0.011  0.012  0.013 Diameter Inches                    Size Number  4  5  6  7  8  9  10  11  12  13 C_(v)  0.00035 0.00061  0.00086  0.0012  0.0015  0.0019  0.0025  0.0028  0.0034 0.0038 Supply 1  0.075  0.136  0.182  0.269  0.360  0.479  0.593  0.653 0.843  0.962 Pressure—psig 5  0.18  0.33  0.45  0.64  0.85  1.10  1.37 1.15  1.94  2.25 10  0.25  0.47  0.65  0.91  1.21  1.57  1.97  2.14 2.73  3.14 15  0.34  0.59  0.82  1.14  1.53  1.97  2.48  2.67  3.43 3.92 20  0.40  0.70  0.97  1.38  1.80  2.33  2.92  3.16  4.07  4.64 25 0.47  0.82  1.12  1.59  2.08  2.69  3.37  3.62  4.66  5.30 30  0.53 0.92  1.26  1.80  2.37  3.03  3.81  4.09  5.23  5.98 40  0.64  1.15 1.56  2.22  2.92  3.75  4.68  5.02  6.44  7.31 50  0.76  1.37  1.86 2.67  3.50  4.45  5.55  5.93  7.59  8.62 60  0.89  1.59  2.16  3.09 4.05  5.13  6.40  6.84  8.75 10.0 70  1.02  1.82  2.46  3.54  4.60 5.83  7.27  7.76  9.92 11.3 80  1.14  2.04  2.75  3.96  5.15  6.53 8.12  8.67 11.1 12.6 90  1.27  2.27  3.05  4.41  5.70  7.20  8.96  9.5612.2 13.9 100  1.40  2.48  3.35  4.83  6.25  7.88  9.81 10.5 13.4 15.3Vacuum 5  0.113  0.203  0.273  0.405  0.536  0.703  0.860  0.953  1.23 1.40 Level In. Hg. 10  0.145  0.263  0.356  0.521  0.687  0.892  1.10 1.20  1.55  1.77 Chocked 15  0.158  0.284  0.392  0.568  0.744  0.964 1.20  1.30  1.68  1.91 Flow 20  0.158  0.284  0.392  0.568  0.744 0.964  1.20  1.30  1.68  1.91 30  0.158  0.284  0.392  0.568  0.744 0.964  1.20  1.30  1.68  1.91 0.014 0.015  0.016  0.017  0.018  0.019 0.020  0.021  0.022  0.023  0.024  0.025 14 15 16 17 18 19 20 21 22 2324 26 0.0043 0.0050  0.0055  0.0067 00.73  0.0080  0.0088  0.0096  0.011 0.012  0.13  0.014 1.11 1.30  1.40  1.64  1.82  2.03  2.22  2.39  2.73 2.99  3.26  3.54 2.56 2.99  3.26  3.73  4.20  4.70  5.23  5.62  6.29 6.87  7.48  8.12 3.56 4.13  4.26  4.79  5.38  6.00  6.70  7.48  9.1710.1 11.0 11.8 4.45 5.17  5.30  6.04  6.84  7.56  8.50  9.34 11.3 12.613.6 14.7 5.28 6.08  6.29  7.20  8.18  9.03 10.3 11.1 13.5 14.7 16.117.3 6.06 6.95  7.25  8.31  9.43 10.4 11.8 12.7 15.5 16.8 18.3 19.9 6.807.82  8.20  9.39 10.7 11.8 13.4 14.4 17.4 19.0 20.7 22.5 8.33 9.56 10.111.6 13.2 14.5 16.5 17.8 21.4 23.3 25.4 27.5 9.83 11.3 12.1 13.8 15.717.3 19.6 21.2 25.2 27.5 30.1 32.6 11.3 13.0 14.0 16.0 18.2 20.0 22.724.6 29.2 31.8 34.7 37.5 12.8 14.7 16.0 18.2 20.7 22.9 25.9 28.0 33.136.0 39.2 42.6 14.3 16.5 17.9 20.5 23.3 25.6 29.0 31.6 37.1 40.3 43.947.7 15.9 18.3 19.9 22.7 25.9 28.4 32.2 35.0 40.9 44.5 48.5 52.8 17.420.0 21.8 25.0 28.4 31.1 35.2 38.1 44.7 48.7 53.2 58.1 1.64 1.90  2.07 2.41  2.70  2.99  3.28  3.60  4.03  4.45  4.87  5.25 2.06 2.37  2.62 2.99  3.35  3.79  4.15  4.62  5.17  5.68  6.12  6.63 2.26 2.59  2.86 3.28  3.71  4.11  4.64  4.92  5.53  6.04  6.61  7.08 2.26 2.59  2.86 3.28  3.71  4.11  4.64  4.92  5.53  6.04  6.61  7.08 2.26 2.59  2.86 3.28  3.71  4.11  4.64  4.92  5.53  6.04  6.61  7.08

The discharge gas from the controlled discharge gas vent can be coupledto a sensor or analyzer. For example, in order to further controlcorrosion, oxygen gas that is contained in the fire sprinkler systempiping network, for example as part of pressurized air, can be displacedwith dehumidified air or nitrogen gas from a nitrogen generator.Likewise, water vapor contained in the pressurized piping network can bedisplaced by dehumidified air or dry nitrogen from the nitrogengenerator, for example. Determining the composition of the gas containedwithin the fire sprinkler system piping network can provide evidencethat the displacement process is progressing. For example, it is notreadily feasible to measure the level of nitrogen in gas as the inertnature of the nitrogen gas molecule means it does not readily react withother elements. Accordingly, the level of nitrogen in the pipeline canbe derived indirectly by measuring the level of oxygen in the pipeline.

The oxygen sensor may be used to measure effective displacement ofoxygen during the initial setup or installation of the system, followingactuation or testing of the system, and/or for monitoring the systemwhile in service. For example, in a dry pipe sprinkler system, one ormore oxygen sensors may be connected to the piping network to ascertainwhether pressurized nitrogen supplied by the nitrogen generator haseffectively displaced oxygen in the system to below a predeterminedthreshold or to a level where oxygen is no longer detectable. The oxygensensor may also be used in an automated system to trigger the nitrogengenerator to purge or flush the system or the system may be manuallyactivated based on a reading provided by the oxygen sensor. For example,the oxygen sensor may be coupled to an alarm indicating that oxygen ispresent or at an undesirable level within the fire protection system. Inthe case where the system is automated, the oxygen sensor may also becoupled to a pressure monitor and may trigger the breathing process tosustain pressure above the low limit pressure (e.g., above the trippressure) by supplying additional nitrogen gas and/or trigger thebreathing process to purge any buildup of oxygen while maintaining thepressurized system between the low limit pressure and the high limitpressure.

As described, the volume of the gas being discharged from the firesprinkler system piping network from one of the controlled discharge gasair vents can be split into a “high flow” stream and a “low flow”stream, where the “low flow” stream can be used to take the oxygenmeasurement. For example, the “low flow” stream may provide a continuousflow for the oxygen measurement. A mechanical valve such as an electricsolenoid valve can be placed on the “high flow” stream and any othervents on the system. When the oxygen sensor achieves the desired oxygenconcentration for the desired time period, a signal can be sent to theelectric solenoid valve(s) to close off the “high flow” stream and anyother vents on the system. This can allow for lower energy consumptionand lower maintenance costs to support the lower oxygen levels withinthe system.

Oxygen analyzers are commercially available that can accuratelydetermine the weight percent of oxygen in a gas sample. Oxygen analyzersare available as hand held manual analyzers that capture samples at apoint in time or as continuous analyzers that continuously monitor thedischarge gas composition. Oxygen analyzers typically require a flowingstream of the gas that is being sampled in order to measure the level ofoxygen in that gas. Suitable oxygen sensors include those provided by:GE Sensing—Panametrics (Billerica, Mass.), built in oxygen analyzers;Maxtec (Salt Lake City, Utah), handheld oxygen analyzers; and AMI(Huntington Beach, Calif.), built in oxygen analyzers.

Also, the water vapor contained in the pressurized piping network can bedetermined by detecting the humidity in the gas being vented from thevents. This allows for the continuous analyzing of the discharge gaswhen dehumidified air is being used to control corrosion within thepiping system, for example. Humidity sensors include resistive,capacitive, and thermal conductivity sensing technologies. Suitablehumidity sensors include those provided by: America Humirel, Inc.(Dearborn Heights, Mich.), Honeywell Sensing and Control (Golden Valley,Minn.), and Sensirion Inc. (Westlake Village, Calif.).

As described, the volume of gas that is being discharged from the firesprinkler system piping network during the breathing process iscontrolled by one or more controlled discharge gas vents. The ventprovides controlled discharge of a metered amount of gas from the firesprinkler system piping network. Any sample stream of the fire sprinklersystem piping network gas for analysis can be considered as part of theoverall gas discharge equation, with respect to the breathing cycle andthe calculations illustrated in Table 1, for example. All or a portionof the discharge gas stream being exhausted from the vent can be used toprovide a sample stream for the continuous gas analyzer. For example,the oxygen sensor and/or humidity sensor can be coupled to abackpressure regulator that always allows a “low flow” stream to pass sothat the sensor is provided with a continuous gas stream formeasurement. Alternatively, the sensor may be coupled to the ventupstream of the backpressure regulator using tubing and/or an orificethat provides a continuous “low flow” stream of gas to the sensor, whilethe backpressure regulator passes a “high flow” of gas when pressure isabove a set threshold.

Table 5 illustrates features of an accurate and stable oxygen sensoruseful to measure the oxygen content of pressurizing gas in dry andpreaction fire sprinkler systems. The complete sensor can be built intoan enclosure and fixed to a wall in the area of the fire sprinklersystem piping network being monitored. The sensor also may be connectedto the building management system and/or provide a visual read-out atthe sensor unit.

TABLE 5 Oxygen Sensor Features Sensor Type: Zirconium Oxide ExpectedLife: 10 years Drift: Negligible Measured range: 0.1% to 25% oxygen byvolume Response time (90% of full 2 seconds scale):Accuracy/Reproducibility: ±0.25%/0.1% Temperature compensation: Notrequired Pressure compensation: Not required Sample connection: tubingQuick connect for 5/32″ Sample flow: Set and conditioned by the ventSample pressure: Atmospheric Input Voltage: In the range +7 to +30 VDC,typically +24 VDC Power Consumption: up to 3 watts Signal output: 0 to5VDC, linear with measured range Dimensions: 9″(230 mm) wide, 11″ (280mm) tall, 4.5″ (114 mm) deep Weight: 11 lb (5 kG) Power & SignalConnection: Through ⅞″ diameter port (for ½″ conduit connector)

Shown in FIG. 2 is a portion of a fire protection system 200 thatincludes a controlled discharge gas vent and an oxygen sensor with analarm. The fire protection system pipe 205, located for example at theend of a main line or branch line, has a reducer/coupler 210 to join thesystem piping to a line running to an isolation valve 215; e.g., a ballvalve. A coupling union 220 is used to join the line from the isolationvalve 215 to a Y-strainer 225 positioned ahead of a levered float valve230. Running from the levered float valve 230 is an in-line filter 235that is then coupled to an adjustable backpressure regulator 240. One ormore threaded hangers 245 are used to suspend the system 200 within thestructure to be protected. Piping or high pressure tubing 250 runs fromthe metallic orifice 242 to an oxygen sensor 255. At least a portion ofdischarged gas from the regulator 240 is directed through the tubing250. In some cases, a portion of gas is continuously vented from theregulator 240 through the tubing 250 to the oxygen sensor 255. Theoxygen sensor 255 is connected to a power supply 260, e.g., 24V DC or110V, and includes an output signal line 265 running to an alarm (notshown). The sensor 255 can be affixed to a wall, for example, andprovides visual indicators, such as a power “on” lamp 270, alarm lamp275, and a digital output 280 for 02 level.

Other sensors may be used with the controlled discharge gas vent, inaddition to or in lieu of the oxygen sensor. For example, the humidityof pressurized gas within the dry pipe pressurized piping network may bemeasured using a humidity sensor; e.g., electronic hygrometer. In thismanner, the system may manually or automatically perform one or morebreathing cycles, if necessary, to reduce the humidity of thepressurized gas below a predetermined threshold or below detectablelimits.

Various gases may be used in breathing cycles with the dry pipe systemand controlled discharge gas vent. Nitrogen is preferable as it can beused to simultaneously displace oxygen and dry the piping network byremoving water. Nitrogen can also be provided using a nitrogen generatorto enrich nitrogen from air. Likewise, carbon dioxide may be used todisplace oxygen and/or water vapor. However, other gases, such asdehumidified air, may be used to dry the piping network. Or, in somecases, the breathing cycle may be run using just compressed air wherethe ambient air has a relatively low humidity and is capable of dryingthe piping network.

Various combinations of gases may also be employed. In some embodiments,the breathing cycles may initially use compressed air to substantiallydry the piping network following hydrostatic testing, for example, andthen the breathing cycles may shift to using pressurized nitrogen todisplace oxygen and/or any residual water vapor. For the purpose ofcontrolling or mitigating corrosion, any of a variety of dry gases, likedehydrated air, carbon dioxide, or argon, may be used as the purginggas.

In the case of the dry pipe system and controlled discharge gas vent, itis preferable to use nitrogen in the breathing cycles to fill the pipingvoid space, pressurize the piping, and to mitigate the corrosion of theferrous and cuprous metal components. Nitrogen, for example provided bya nitrogen generator, is used to pressurize the system, purge theinitial quantities of oxygen and other gases trapped in the pipingthrough one or more vents in the fire sprinkler system in order to drythe system, and to allow the quantity of nitrogen in the piping toincrease and ultimately approach about 90% or greater following a numberof breathing cycles. For example, the dew point of 95% nitrogen isapproximately −71° F.; accordingly, the nitrogen will absorb moisture inthe piping left from hydrostatic or other types of system testing orfrom condensation of saturated compressed air that had previously filledthe pipe. The breathing process allows the nitrogen/air mixture toabsorb water and carry it out of the system through the vent point(s),leaving the system in a significantly dryer state, while simultaneouslydisplacing oxygen.

Dry pipe sprinkler systems including the controlled discharge gas ventcan be advantageously employed in freezer or refrigerator applicationsor in environments where water may freeze. For example, under conditionswhere water may freeze, ice blocks can form in the sprinkler systempiping network when compressed air containing water or saturated withwater is used to pressurize the piping. As the moisture in thecompressed air condenses in the piping, the water freezes to form icethat may restrict flow or even create an ice block or dam within thepiping, preventing further gas or water flow altogether. Regenerativedesiccant dryers or membrane dryers have been employed to prevent iceblocks from forming. However, flushing and purging with 90% or greaternitrogen, with its low dew point, eliminates the need for theregenerative desiccant or other types of air dryers. What is more, dueto the difficulty of completely removing residual water from a complexsprinkler system, solely using dehumidified air for drying the pipe maynot prevent or significantly reduce corrosion in remaining water filledareas or areas containing residual liquid water or water vapor whichmight later condense to form liquid water. If dry nitrogen is used asthe drying medium, oxygen will also be removed along with the water andwater vapor and corrosion will be substantially reduced or eliminated.

Several factors influence corrosion within a fire protection system. Thenature of the materials used in construction of the system and theirsusceptibility to oxidation directly relate to the damage potential ofoxygen and water. The source water provided to the system may includebiological contaminants, dissolved and/or solid nonbiologicalcontaminants, trapped air, and dissolved gases. A portion of the systemcan be in intermittent contact with liquid water, as is the case for adry pipe or preaction system actuation during routine testing orservicing or when activated by a fire. In some cases, once started thecorrosion process permits or accelerates further corrosion; for example,corrosion by-product (e.g., iron oxide) may be shed, sloughing off toexpose new metal (e.g., iron) to oxidation. These factors andcombinations of these factors can corrode the fire protection system,deteriorating its performance, or even result in system failure.

Fire protection systems are often constructed using ferrous and cuprousmetallic pipes and fittings. Pipe materials typically come from themanufacturer or distributor with associated open-air corrosion on theinternal and external walls. This can include but is not limited to:iron oxide mill scale caused during the manufacturing process bycondensation of water on the metal surfaces and the subsequentgeneralized oxygen corrosion that results from oxygen attack, the metalloss is typically minimal with no significant pitting; debris from thestorage yard on the threads and in the ends of the pipe; and thepresence of other solids associated with outside storage, such as spiderwebs, dead bugs, etc. After or during the installation of the pipe,additional sources of debris and fouling may end up inside the assemblednetwork of piping, including: residual cutting oil from the threadcutting process during installation, metal filings from the threadcutting process during installation, various forms of hydrocarbon basedthread lubricants, and Teflon® tape used in assembly of the pipefittings.

The source water used in the fire protection system is generally from afresh potable water source with very low total dissolved solids (TDS).The water is generally saturated with oxygen from the atmosphere andcontains very little, if any, insoluble suspended solids. It may alsocontain small (less than about 2 ppm) amounts of residual chlorine frommunicipal treatment at the source. The water may not contain anydetectable levels of microorganisms, however, this does not preclude thepresence of microorganisms, as they will simply be difficult to detectat the low levels that exist in the potable water.

Once installed, at least a portion of the fire protection system isfilled and charged with water. In the case of a dry pipe system, thepiping network is filled with water upon routine testing or followingactivation. As the source water fills the piping, all of the debris thatis clinging to the interior walls will become mobilized. Materials thatare insoluble in water (solids) will generally sink to settle andcollect in all of the low spots within the system due to gravity. Forexample, in long runs of horizontal piping, the solids will collect atthe six o'clock position, when viewing a pipe in cross-section. Anyhydrocarbon within the system will float on the water and will tend toagglomerate (i.e., oil wet) any insoluble particulates that arecontacted. It is also difficult to completely remove all of the airduring the water charging process. Air (and water vapor) and liquidwater that is left in the system creates a discrete air/water interface.As the system is pressurized, air will also dissolve into the water andquickly reach a state of equilibrium.

Oxygen corrosion may be the predominant form of corrosion and metal losswithin the fire protection system. Air contains approximately 21%oxygen, and unless the source water is mechanically de-aerated orchemically treated to effect oxygen removal, it will generally containabout 8-10 ppm of dissolved oxygen when it first enters the piping. Theoxygen will immediately react with any free iron it contacts on the pipewalls.

The initial fill of water will remove iron from the pipe walls and somesmall level of metal loss will occur. The metal loss will be most acuteat the air/water interface where the dissolved oxygen content will bethe highest. The soluble iron that is liberated from the pipe walls atthe interface will almost immediately precipitate as iron oxide,probably as ferric oxide, commonly known as rust. The iron oxide mayadhere to the pipe wall for a time, just below the air/water interface,but because of the loose, non-adhesive nature of the deposit, it ishighly likely that the iron oxide will slough off and settle to thebottom of the pipe. Even slight turbulence or disturbances in the pipenetwork will cause the deposit to be shed, exposing new free iron forattack by oxygen. As the air-water-metal environment stagnates, theoxygen will be consumed and corrosion will slow down. If leftundisturbed, the system could remain at a low general corrosion rate fora long period of time.

Several factors may accelerate or continue corrosion of the system,however. These include: addition of more oxygen, solids (e.g., ironoxides, particulate matter, etc.), growth of microbiological organisms,mechanical deposit removal, and draining and refilling the system,including testing or actuating the system. Any oxygen that enters thesystem will affect the equilibrium that exists between iron, water, andoxygen. More oxygen will cause additional free iron loss and create moresolids by precipitating iron oxides. The metal loss at the air/waterinterface will once again become the site producing the most reactionand subsequent corrosion.

Solids accelerate corrosion by several mechanisms. Under-depositacceleration may occur wherein the area under the solid achieves ananodic-character versus the adjacent metal. This anodic-character willmean that corrosion will be more aggressive under the deposit andpitting will occur. In oxygenated systems, the area under the depositcan become oxygen-depleted and can achieve anodic-character versus theadjacent metal. Once again, the corrosion under the deposit will becomemore aggressive and pitting will occur. Solids also provide an idealenvironment for microbiological organisms, such as bacteria, tocolonize. In addition, depending on the chemical make-up, the solids mayserve as nutrient sources for the bacteria. Slimes and deposits that thebacteria create will also act as deposits under which pitting may occur.

There are a myriad of different mechanisms that come under the headingof microbiologically influenced corrosion (MIC). Generally, MIC refersto corrosion that is effected by the metabolic processes of mixedcultures of microorganisms, typically bacteria and fungi. For example,microorganisms can act to influence corrosion in three different ways.First, microorganisms can produce slimes and deposits that acceleratethe under-deposit corrosion mechanisms; e.g., oxygen concentration cellsin aerobic environments. Second, microorganisms produce metabolicby-products that directly contribute to the corrosion reaction; e.g.,organic acid producers that solubilize the iron in mild steel. Third,microorganisms produce metabolic by-products that indirectly contributeto the corrosion reaction by acting as a cathodic depolarizer; e.g.,sulfides produced by sulfate-reducing bacteria.

Depending on the type of bacteria that are involved the corrosion ratein the system can be accelerated by the following mechanisms: (1) slimeformation—under-deposit pitting corrosion; (2) acid production—acidicpitting corrosion; and (3) sulfide anion production—cathodicdepolarization resulting in pitting corrosion.

Mechanical deposit removal can allow additional corrosion. Anytime acorrosion deposit is removed from the metal surface, it creates a newsite for attack. This will most often occur at the air/water interfaceand repeated removal of the deposit will create crevices.

Draining and refilling the system also allows additional corrosion. Eachtime the system is drained of the fluids and refilled, the high rate ofoxygen corrosion that exists with a fresh supply of air will remove anew layer of iron from the pipe walls. Any deposits that exist on themetal surfaces will become oxygen concentration cells in the new oxygenrich fluids and the otherwise low general rate of corrosion will begreatly accelerated and pitting will occur.

In some embodiments, the fire protection system and controlled dischargegas vent can utilize a nitrogen generator to introduce nitrogen into thesystem to displace any oxygen via the described breathing cycle(s). Thenitrogen generator can provide nitrogen on-demand to fill and/or purge asystem as desired, automatically based on a sensor, such as an oxygensensor, on a periodic basis, or on a continuous basis. Nitrogengenerators and features relating to nitrogen generators include those asdescribed in International Application No. PCT/US09/56000, Burkhart etal., filed Sep. 4, 2009.

In the case of a dry pipe sprinkler system, the nitrogen generator maybe used to purge or recharge the pressurized piping network withnitrogen. For example, pressurized nitrogen within the piping networkholds the dry pipe valve in the closed position to prevent entry of thepressurized water into the piping network. Any leaks in the sprinklersystem may cause a loss of pressure. The nitrogen generator maytherefore be used to recharge the pressurized piping network as neededand may be configured to do so automatically. For example, the fireprotection system may include a pressure gauge to measure the nitrogenpressure against the dry pipe valve. The nitrogen generator mayautomatically provide pressurized nitrogen when the pressure gauge dropsbelow a predetermined threshold. In this way, the nitrogen generator canautomatically maintain the pressure above the low limit, which is abovethe trip pressure of the dry pipe valve, by supplying additionalpressurized nitrogen as needed.

The fire protection system and controlled discharge vent may also beconfigured to continuously supply pressurized nitrogen into the pipingnetwork using the nitrogen generator, where the breathing cycles allowthe pressure to slowly ramp between the low and high limits. In thiscase, the nitrogen generator provides a steady stream of pressurizednitrogen into the piping network to keep the dry pipe valve closed. Toallow for continuously supplied pressurized nitrogen gas to enter thesystem, the controlled discharge gas vent opens. Pressurized nitrogen isvented while maintaining enough pressure within the system to preventthe dry pipe valve from opening. In the event the fire protection systemis actuated, due to a fire or for testing, the pressure within thepiping network is lost faster than the nitrogen generator can replaceit, even when continuously applying pressurized nitrogen, therebyallowing the dry pipe valve to open and pressurized water to enter thepiping network.

Continuous venting of the fire protection system using one or morecontrolled discharge gas vents facilitates removal of any oxygen withinthe system while maintaining the required system pressure (of nitrogen)for the fire sprinkler system. In dry or preaction fire sprinklersystems, 90%+nitrogen gas (dew point of −70° F.) may also be used todehydrate the system by pulling any water within the system into the drynitrogen and venting the gas, thereby eliminating residual water, one ofthe key components in the corrosion reaction.

The present systems and methods can be used in conjunction with othercomponents and methods in order to further reduce corrosion or treatcorrosion and the effects of corrosion. For example, fire protectionsystems can be sterilized to control bacteria using chemical treatmentsand/or heated gases or liquids. Solids may be eliminated by cleaning andflushing the system. Corrosion can also be reduced in fire protectionsystems through the application appropriate corrosion inhibitingchemicals that are applied to the water that enters the fire protectionsystem piping.

Corrosion inhibitors are commercially available that can significantlyreduce the rate of oxygen corrosion in ferrous and cuprous metals. Thecorrosion inhibitors are generally proprietary formulations that retardthe cathodic half reaction of the corrosion cell. There are alsoproprietary formulations that can be used to provide biocidal activitywherein the microbes within the fire sprinkler system piping are killedby exposure to toxic levels of the biocidal formulations. These productsindirectly reduce the level of corrosion by preventing the proliferationof microorganisms and thereby preventing their corrosion acceleratingactivities including cathodic depolarization, under-deposit accelerationor organic acid attack of the ferrous or cuprous metallic components. Inevery instance, the use of nitrogen augments the reduction in corrosionthat can be afforded through the use of corrosion inhibiting chemicalsor microbiocidal chemicals.

The fire protection system and controlled discharge gas vent provideseveral benefits and advantages. For example, breathing cycles employingdisplacement of oxygen with nitrogen reduce or eliminate the primarycorrosive specie within the aqueous environment that exists in a firesprinkler system. Nitrogen can be applied whenever the system is testedor recharged or following actuation in the event of a fire. For example,each time the fire protection system is breached for annual testing orsystem modification, nitrogen is added to displace oxygen to preventcorrosion.

Nitrogen is preferred for use in the breathing cycle as it has manybeneficial characteristics for use within a fire protection system. Itis inert and will not participate, augment, support, or reinforcecorrosion reactions. It can be used as a stripping gas to remove oxygenfrom the water and/or from the void space above the water with adequateventing. If venting is continued, the concentration of oxygen in thewater and in the void space can be reduced to near zero. Nitrogen isnon-toxic, odorless, colorless, and very “green,” as it is not agreenhouse gas and may be generated on site and on-demand from air usinga nitrogen generator. Where the fire protection system is coupled to amunicipal water supply, with nitrogen there is no concern about toxicityor contamination of the water supply should any backflow occur from thefire protection system to the municipal water, as might be the case withother chemical additives. What is more, any water treated with nitrogenthat must be discharged into the municipal sewer system is non-toxic andwill contain little or no iron oxide resulting from corrosion of thepiping. The present systems and methods using nitrogen also reduce oreliminate oxidation and degradation of elastomeric seats found in valvesand other components of the fire protection system.

Nitrogen displacement of oxygen can also serve to inhibit growth ofaerobic microbiological organisms within the fire protection system andmay even result in death of these organisms. Aerobic forms of microbialcontaminants generally pose the greatest risk of creating slimes infresh water systems. These slimes pose serious risks to fire sprinklersystems because they can impact the hydraulic design of the firesprinkler system if they form in sufficient quantities as sessile(attached) populations. These slimes can also slough off of the pipewalls and lodge in sprinklers and valves. The present systems andmethods substantially reduce or even eliminate growth of these aerobicmicrobiological organisms and prevent subsequent slime formations.

The present systems and methods employ a nitrogen generator thatprovides several advantages. Nitrogen generators are a cost-effectivemeans for continuous administration of nitrogen to the fire protectionsystem. They obviate the need for gas cylinder inventory, changing outof gas cylinders, and risks associated with handling gas cylinders.Nitrogen generators only require a compressed air supply to separateatmospheric nitrogen from oxygen.

The present technology is further described in the following example.The example is illustrative and does not in any way limit the scope ofthe technology as described and claimed.

Example 1—Breathing Dry Pipe System

An embodiment of a fire protection system comprises a dry pipe sprinklersystem and one or more controlled discharge gas vents that are operableto breathe and displace oxygen and water vapor. The dry pipe sprinklersystem utilizes water as an extinguishing agent. The system piping fromthe dry pipe valve to the fusible sprinklers is filled with pressurizednitrogen. In some cases, the system is an air check system or furtherincludes an air check system. An air check system is a small dry systemwhich is directly connected to a wet pipe system. The air check systemuses a dry valve and a nitrogen generator but does not have a separatealarm. The alarm is provided by the main alarm valve.

A dry pipe system is primarily used to protect unheated structures orareas where the system is subject to freezing. Under such circumstances,it may be installed in any structure to automatically protect thestructure contents and/or personnel from loss due to fire. The structuremust be substantial enough to support the system piping when filled withwater. The system should be designed by qualified design engineers inconjunction with recommendations from insuring bodies.

The dry pipe system may include several components. Although various drypipe systems constructed according to the present teachings willfunction in the same manner, the components and arrangements may varydue to the application of different sets of standards. For example, thesize and geometry of the fire protection system is based on theparticular installation and coverage.

The water supply includes an adequate water supply taken from a citymain, an elevated storage tank, a ground storage reservoir and firepump, or a fire pump taking suction from a well and pressure tank.

Underground components include piping of cast iron, ductile iron orcement asbestos; control valves and/or post indicator valves (PIV); anda valve pit. The valve pit is usually required when multiple sprinklersystems are serviced from a common underground system taking supply froma city main: two OS & Y valves, check valves or detector check, firedepartment connection (hose connection and check valve with ball drip).Depending on local codes for equipment and building requirements, aback-flow preventer, full-flow meter, or combinations of equipment maybe required.

Auxiliary equipment includes fire hydrants with outlets for hose lineand/or fire truck use.

Portions of the system inside the structure include the following. Acheck valve must be incorporated if not already provided in theunderground system. A control valve, such as a wall PIV or OS&Y must beincorporated if a control valve is not already provided in theunderground piping for each system. A dry pipe valve with the followingfeatures: the dry-pipe valve and pipe to the underground system must beprotected from freezing, for example, the structure or enclosure shouldbe provided with an automatic heat source, lighting, and sprinklerprotection; a nitrogen generator (automatic or manual) capable ofrestoring nitrogen pressure to the system in 30 minutes or less; anaccelerator is required when system capacity exceeds 500 gallons (1892.7liters); a water motor alarm or electric pressure switch; and valve trimand pressure gauges.

Fire department connection to the system is provided by a hoseconnection and check valve with a ball drip, if it is not alreadyprovided as part of the underground components.

The system piping progressively increases in size in proportion to thenumber of sprinklers from the most remote sprinkler to the source ofsupply. The pipe size and distribution is determined from pipe schedulesor hydraulic calculations as outlined by the appropriate standard forthe hazard being protected.

Sprinklers include various nozzles, types, orifice sizes, andtemperature ratings, as known in the art. Sprinklers installed in thependent position must be of the dry pendant type when the piping andsprinkler are not in a heated area that may be subject to freezingtemperatures. Sprinklers are spaced to cover a design-required floorarea.

The system includes an inspector's test and drain components. A testdrain valve must be provided. All piping is pitched toward a drain. Adrain is provided at all low points. A two-valve drum drip may berequired. An inspector's test is required on each system. Theinspector's test simulates the flow of one sprinkler and is used whentesting the system to ensure that the alarm will sound and the waterwill reach the farthest point of the system in less than one minute.

The system includes various pipe hangers as needed.

The point of incorporation for the nitrogen discharge from the nitrogengenerator is typically at a point just above the dry pipe valve on themain riser. The point of entry into the piping is a pipe equipped with acheck valve to prevent backflow to the nitrogen generator.

One or more controlled discharge gas vents with oxygen sensors arepositioned in the piping network. The vents are positioned at or nearthe end of a length of pipe in the piping network. In this way, when thepiping network is filled with pressurized nitrogen for service or whenthe piping network is purged with nitrogen for drying after testing oractuation, the vent and sensor are used to ensure that all or anappropriate level of oxygen is displaced as the nitrogen stream isallowed to exit a terminal vent within the piping network.

The fire protection system operates as follows. When a fire occurs, theheat produced will operate a sprinkler causing the nitrogen pressure inthe piping system to escape. When the pressure trip-point is reached(directly or through the accelerator), the dry-pipe valve opens allowingwater to flow through the system piping and to the water motor alarm orelectric pressure switch to sound an electric alarm. The water willcontinue to flow and the alarm will continue to sound until the systemis manually shut off. A dry-pipe valve equipped with an accelerator willtrip more rapidly and at a higher air-pressure differential. Componentparts of the dry-pipe system operate in the following manner.

The dry valve operates as follows. When the nitrogen pressure in the drysystem has dropped (from the fusing of an automatic sprinkler) to thetripping point of the valve, the floating valve member assembly (airplate and water clapper) is raised by the water pressure trapped underthe clapper. Water then flows into the intermediate chamber, destroyingthe valve differential. As the member assembly rises, the hook pawlengages the operating pin which unlatches the clapper. The clapper isspring-loaded and opens to the fully opened and locked positionautomatically.

The accelerator operates on the principal of unbalanced pressures. Whenthe accelerator is pressurized, nitrogen enters the inlet, goes throughthe screen filter into the lower chamber and through the anti-floodassembly into the middle chamber. From the middle chamber the nitrogenslowly enters the upper chamber through an orifice restriction in thecover diaphragm. In the SET position the system nitrogen pressure is thesame in all chambers. The accelerator outlet is at atmospheric pressure.When a sprinkler or release operates, the pressure in the middle andlower chambers will reduce at the same rate as the system. The orificerestriction in the cover diaphragm restricts the nitrogen flow from theupper chamber causing a relatively higher pressure in the upper chamber.The pressure differential forces the cover diaphragm down pushing theactuator rod down. This action vents the pressure from the lower chamberto the outlet allowing the inlet pressure to force the clapper diaphragmopen. The pressure in the accelerator outlet forces the anti-floodassembly closed, preventing water from entering the middle and upperchambers.

On a dry pipe system, the nitrogen pressure from the accelerator outletis directed to the dry pipe valve intermediate chamber. As the nitrogenpressure increases in the intermediate chamber, the dry valve pressuredifferential is destroyed and the dry valve trips allowing water toenter the dry pipe system. On a pneumatic release system, the outletpressure is vented to atmosphere, speeding the release system operation.

With reference to FIG. 3, a dry pipe fire protection system operable toperform one or more breathing cycle is shown 300. A city main 301provides pressurized water to the underground fire main 303 and to afire hydrant 305. A key valve 307 is used to control flow of water intothe underground fire main 303 and a post indicator valve 309 indicateswater flow is available to the system. The system also includes a testdrain 311, a ball drip 313, and a fire department connection 315. Acheck valve 317 positioned near the fire department connection 315prevents backflow from the system back into the fire departmentconnection. A water motor alarm drain 319 runs from the water motoralarm 327 and a test drain valve 321 controls flow to the test drain311.

A dry pipe valve 323 controls pressurized water flow from theunderground fire main 303 to the cross main 329 and the piping networkin response to pressurized nitrogen within the piping network. Anitrogen generator 325 is connected past the dry pipe valve 323 on thecross main 329 and piping network side and uses a check valve 326 toprevent backflow into the nitrogen generator 325. A pressure maintenancedevice 331 is used to measure nitrogen pressure in the piping network.An alarm test valve 333 and drain cup 335 can be used for testing.Another check valve 337 is positioned to prevent backflow from thesystem into the underground fire main 303. A drum drip 339 and drainvalve and plug 341 are positioned in the piping network.

One or more upright sprinklers 343 and pendent sprinklers 345 arepositioned and spaced within the piping network to provide fireprotection coverage. An inspector's test valve 347 and an inspector'stest drain 349 are positioned at a terminal portion of the pipingnetwork to allow testing and purging of the system. One or morecontrolled discharge gas vents 351 are positioned close to ends ofpiping network lines, for example, near the inspector's test valve 347and inspector's test drain 349, adjacent to system vents and at otherterminal portions of the piping network. The controlled discharge gasvents 351 are coupled to a sensor 352, such as an oxygen sensor and/orhumidity sensor, which is used to measure exhaust gas from within thesystem to ensure all oxygen and/or water vapor or an acceptable level ofoxygen and/or water vapor is purged from the system.

The embodiments and the examples described herein are exemplary and notintended to be limiting in describing the full scope of apparatus,systems, and methods of the present technology. Equivalent changes,modifications and variations of some embodiments, materials,compositions and methods can be made within the scope of the presenttechnology, with substantially similar results.

1. A controlled discharge gas vent comprising: a liquid sensing valvehaving an inlet and an outlet; a back pressure regulator having an inletand an outlet, wherein the inlet of the back pressure regulator iscoupled to the outlet of the liquid sensing valve; and a first orificehaving an inlet and an outlet and operable to provide a flow rate of gastherethrough, wherein the inlet of the first orifice is coupled to theoutlet of the back pressure regulator.
 2. The controlled discharge gasvent of claim 1, further comprising a sensor selected from the groupconsisting of an oxygen sensor, a humidity sensor, and combinationsthereof.
 3. The controlled discharge gas vent of claim 2, wherein theoxygen sensor is operable to sense oxygen from a continuous flow of gasand the humidity sensor is operable to sense water vapor from acontinuous flow of gas.
 4. The controlled discharge gas vent of claim 2,wherein the sensor is coupled to the outlet of the first orifice.
 5. Thecontrolled discharge gas vent of claim 4, wherein the back pressureregulator is operable to continuously provide a low flow of gas to theorifice and provide a high flow of gas to the orifice upon reaching apressure threshold.
 6. The controlled discharge gas vent of claim 2,further comprising a second orifice having an inlet and an outlet andoperable to provide a flow rate of gas therethrough that is lower thanthe flow rate of gas through the first orifice, the inlet of the secondorifice coupled to the outlet of the back pressure regulator, and theoutlet of the second orifice coupled to the sensor.
 7. The controlleddischarge gas vent of claim 2, further comprising a second orificehaving an inlet and an outlet and operable to provide a flow rate of gastherethrough that is lower than the flow rate of gas through the firstorifice, the inlet of the second orifice coupled to the coupling of theliquid sensing valve outlet and the back pressure regulator inlet, andthe outlet of the second orifice coupled to the sensor.
 8. Thecontrolled discharge gas vent of claim 1, further comprising aY-strainer having an inlet and an outlet, the outlet of the Y-strainercoupled to the inlet of the liquid sensing valve.
 9. The controlleddischarge gas vent of claim 8, further comprising a coupling unionhaving an inlet and an outlet, the outlet of the coupling union coupledto the inlet of the Y-strainer.
 10. The controlled discharge gas vent ofclaim 9, further comprising a ball valve having an inlet and an outlet,the outlet of the ball valve coupled to the inlet of the coupling union.11. The controlled discharge gas vent of claim 1, further comprising agas sampling positioned within the coupling of the liquid sensing valveoutlet and the back pressure regulator inlet.
 12. The controlleddischarge gas vent of claim 1, further comprising an in-line filterpositioned within the coupling of the liquid sensing valve outlet andthe back pressure regulator inlet.
 13. The controlled discharge gas ventof claim 1, wherein the pressure threshold of the back pressureregulator is adjustable.
 14. The controlled discharge gas vent of claim1, further comprising a muffler having an inlet and an outlet, the inletof the muffler coupled to the outlet of the orifice.
 15. A fireprotection system comprising: a sprinkler system comprising: at leastone sprinkler; a source of pressurized water; a piping networkconnecting the at least one sprinkler to the source of pressurizedwater; and a controlled discharge gas vent according to claim 1; and asource of pressurized gas coupled to the sprinkler system.
 16. The fireprotection system of claim 15, wherein the sprinkler system is a drypipe system or a preaction system.
 17. The fire protection system ofclaim 15, wherein the source of pressurized gas is selected from thegroup consisting of an air compressor, a nitrogen generator, andcombinations thereof.
 18. A method of reducing corrosion in a fireprotection system, the fire protection system comprising a dry pipesprinkler system coupled to a source of pressurized gas, the dry pipesprinkler system comprising at least one sprinkler, a source ofpressurized water, a piping network connecting the at least onesprinkler to the source of pressurized water, a dry pipe valve couplingthe source of pressurized water to the piping network, and a controlleddischarge gas vent according to claim 1, the method comprising: (1)pressurizing the piping network with the source of pressurized gas toprovide a pressure that prevents the dry pipe valve from opening; (2)increasing the pressure with the source of pressurized gas to exceed athreshold pressure of the back pressure regulator of the controlleddischarge gas vent, the threshold pressure being greater than thepressure that prevents the dry pipe valve from opening; and (3) ventingpressurized gas via the controlled discharge gas vent by opening of theback pressure regulator until the pressure of the piping network isbelow the threshold pressure of the back pressure regulator.
 19. Themethod of claim 18, further comprising repeating steps (1) and (2). 20.The method of claim 18, wherein the source of pressurized gas isselected from the group consisting of an air compressor, a nitrogengenerator, and combinations thereof.
 21. (canceled)
 22. (canceled) 23.(canceled)
 24. (canceled)